Numerous systems exist for tracking a golf ball and estimating its range. Their main purpose is to give golfers a graphic and/or numeric display indicating their drive's effectiveness when they practice or play.
U.S. Pat. No. 5,303,924 describes a golf game apparatus that simulates a total golf shot distance based upon the actual flight of a struck golf ball at a practice range, projecting the flight distance of the ball to an initial impact position on a target area. A microphone in the area detects the take off of the ball struck by the club head, and an array of microphones in the target area detects its arrival. The time between the two events can be correlated to the range. The system requires a semi-permanent installation.
U.S. Pat. No. 5,413,345 describes a system that identifies, tracks, displays and records all or selected portions of the path of one or more golf balls. It performs these functions from the time each ball is struck, or after it is in flight, until it reaches the final point of rest. It uses an array of high-speed cameras installed on the green.
U.S. Pat. No. 5,472,205 describes a system that detects the club head offset angle relative to a desired club head axis as well as the speed of club head by sensing light reflected from the underside of the club head and processing this information electronically. The latter can be used to calculate the ball's speed by assuming an efficiency of momentum transfer from the club head to the ball. The system requires a semi-permanent installation.
U.S. Pat. No. 5,489,099 describes a system comprising a video camera, a video processor and a flight path predictor. A video camera locks onto the ball and tracks it while being rotated by an automatic control system.
U.S. Pat. No. 5,846,139 describes a golf simulator consisting of three arrays of infrared receivers and emitters installed in an enclosure providing a shield from the ambient light. The system determines the ball's velocity vector. It requires a permanent installation.
U.S. Pat. No. 5,926,780 describes a system for measuring a ball's velocity vector. It consists of two arrays of light sensors illuminated from above by two light sources. When the ball is struck, it flies over the two arrays and casts a shadow over a few sensors. Their location in the array and the position of the light sources allows the calculation of the ball's velocity vector. The patent does not address the exposure of the arrays to the ambient light. The system requires a semi-permanent installation.
U.S. Pat. No. 5,938,545 describes a system comprising two video cameras mounted on a golf cart. Their fields of view overlap and they track the ball by successive frame scans. The ball's trajectory is determined with respect to the cart, which is at an angle with respect to the launch pointer target line and at a certain distance from this reference point. This angle and this distance must both be known in order to relate the trajectory to the target line and to the position of the golfer. The system does not address the saturation effect of the sun on the area CCD sensor in the camera.
U.S. Pat. No. 6,012,987 describes an electronic surveillance camera and a motion sensor above the green. Signals from the camera and the motion sensor are transmitted to a processing unit. The latter generates the movement of an object on a video screen. The system requires a semi-permanent installation.
U.S. Pat. No. 6,093,923 describes two or more video cameras installed on a drive range tracking a golf ball within their fields of view. The system then electronically simulates the ball's trajectory to determine the ball's probable point of impact.
U.S. Pat. No. 6,520,864 describes a video camera tracking a golf ball against a stationary background. A computer processes the video signal to detect the golf ball and to automatically determine its trajectory.
Reference [1]: Barras, Ch., Localisation optique d'objets rapprochés animés d'une grande vitesse (Optical location finding of high-velocity objects at close range), Institut franco-allemand de recherche de Saint-Louis (Franco-German Research Institute Saint-Louis), report S-R 904/92. Though arising in a field unrelated to the tracking of out-going objects, this reference [1] describes a system for protecting a military vehicle consisting of a pair of photodiode arrays with lenses that form fan-shaped fields of view overlapping in a single plane. It can detect at close range the position of an incoming projectile aimed at a vehicle. However, it cannot determine the velocity, nor the direction of the threat.
Reference [2]: European patent application by Giat Industries, EP 1 096 219 A1. Inventors: Lefebvre, Gérald and Muller, Sylvain; Procédé et systéme pour détecter une menace tirée sur un objet fixe ou mobile. (Method and system for detecting a threat fired at a stationary or moving object). Applicant, Publication date: May 2, 2001. This reference [2] describes a similar military-focus system concerning incoming objects in which two arrays with lenses installed on either side of the front of a military vehicle define four vertical intersecting fields of view. It explains how measuring the time when a projectile penetrates each planar field of view and knowing the angle between the lines joining the penetration points to the sensors, on the one hand, and the horizontal plane, on the other hand, provides sufficient information for calculating the position of the projected penetration points and the velocity vector of the incoming projectile. This system covers only a military application related to the calculation of an incoming projectile's position and velocity vector, wherein the trajectory is assumed to be linear. This reference relies upon making four successive time measurements. This reference does not address the determination of the path of an outgoing object, much less determining a projected trajectory calculated as a parabola corrected for aerodynamic drag. Furthermore, this patent application does not mention how to prevent the over saturation of the diode array when the image of the sun is focused on it.
There is a need for a sports training system for tracking an object in space that does not require a semi-permanent installation, but can be set up and ready for use in a short time and within a limited space. Such a system can facilitate the training of golf players, baseball players, tennis players and players of other sports based upon control of a projectile. The device could also be used in the evaluation of the mechanical properties of a baseball bat, golf club, tennis racket, or other device used for striking an incoming projectile.
Imaging systems can form an image of an object on a planar surface, as in the case of a charge-coupled device, CCD, employed in a video camera. Such planar images require time to sample all of the pixels available in an x, y array. Simpler imaging systems utilize a linear array that provides a far smaller number of pixel sensors. The sampling time is accordingly substantially reduced. However, such known linear arrays can only sample a planar surface in space, viewed edge-on.
Such linear arrays can be provided with directed pixel sensors, aligned to divide the surface of the viewing plane into a discrete number of viewing sectors. Thus an 82.4-degree field of view divided amongst 512 directed pixel sensors will allow each directed sensor to detect an object present within a detection zone having an average angular dimension of 0.161 degrees within the detection plane.
While providing some image information with respect to the location of an object in space, the full location of an object, much less its trajectory, cannot be defined through use of a single linear array of directed pixel sensors. This invention addresses a method by which multiple linear arrays having directed pixel sensors may be utilized to obtain more information about the location of an object, and according to variants, defining not only its instantaneous location in space, but also its path of travel, local velocity and ultimate trajectory.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.